After extensive on-track testing, we can announce our center-mount fan housing insert to be a success, and our 36hp design to need slightly more refinement. The 36hp design is not an insert, but a blower housing body unto itself.

Curved ducting inside our fan housing distributes the cooling air in a more uniform way than factory, and this is not to say the German engineers had it wrong. They were designing for the lowest cost vs the highest efficiency. Even so, the factory compromises for cylinder #3 are well know, and at no time did they anticipate the engine temperatures of the custom made, high performance engines we run today.

The 36hp design is different from a steel housing first in that is made of ABS plastic, and is a true racing part, not a modified street part. It is not designed to last for decades. It purpose is to save weight (on the heavy end of the car) and provide uniform cooling airflow to both cylinder banks equal to or better than its steel counterpart.

Top view of the 36hp housing shows it has no top strip. It doesn't need one as the ducting is completely enclosed. The housing is strong enough to handle generator or alternator vibration, but does not support mounting an ignition coil.

The primary refinement we discovered necessary for the 36hp design was an increase in clearance between the lower air ducting and an oil cooler blockoff plate or an oil in/out adapter. Which requires a re-curving of the ducting. Luckily, our computerized CNC machine can handle this.

Bottom view. The lower ducting curves are being recontoured without loss of air flow.

Our plastic ducted insert for the center-mount aluminum fan housing has performed without trouble through several serious races now.

To be worth our time, these fan housings have to have a demonstrable advantage.I like the reduced weight, since the metal housings are heavy and these ABS housings are ounces. The really good feature is the ducted air. It's to air as polarization is to light. Focused.

Actually, I thought as thin as we make the ABS, the edges within the cylinder shrouds, just above the heads and cylinders, would warp. It hasn't happened yet.

We have another temperature testing session coming up on the engine stand with the modified 36hp housing.

To be worth our time, these fan housings have to have a demonstrable advantage.I like the reduced weight, since the metal housings are heavy and these ABS housings are ounces. The really good feature is the ducted air. It's to air as polarization is to light. Focused.

Actually, I thought as thin as we make the ABS, the edges within the cylinder shrouds, just above the heads and cylinders, would warp. It hasn't happened yet.

We have another temperature testing session coming up on the engine stand with the modified 36hp housing.

FJC

Gotta question and it is driven by vacuum toilets . The air flow in directed areas like in the fan housing, did you put a clear cover over the mock up and use the cotton tails to check air flow? I remember that being a problem with some of the other aftermarket units in the past.

Not picking but more like being interested in the process. I did work on vacuum toilets on the airplanes and the engineers spent a lot of time in the wind tunnel (no pun or grossness implied) just to get the right shape of the bowl so they would get full cleaning of the toilet bowl by the vacuum. It made the news back in the early to mid-90s.

Everything you have said sounds first class. The metal fan housing are not only heavy but awkward too. Again, I was just asking for my knowledge. It might be something I would be interested in a farther along in this build if it will take some bouncing around .

I have two enterprises, a software company and RetroRacing. Only modesty prevents me from disclosing that one of my software applications runs major racing events such as Daytona, Sebring, Road Atlanta, etc. On the pure tech side, I have designers and engineers who create custom hardware for access control, anti-tamper, etc, applications. There is some overlap in resource usage because we have software and hardware for racing.

Our designer used some air conditioning flow/pressure equipment to test our fan housing volume and velocity.

We have a retired fluid dynamics engineer on staff, "Paul Ray The Rocket Scientist" who worked on NASA projects. He really didn't do anything with rockets, except for their launching facilities plumbing. He advises us on air scoops, oil system plumbing and their esoterics, ad nausem. If you want to get an hour lecture on a specific 90-degree AN fittings flow and swirl control, ask Paul Ray.

Anyway, Paul Ray and the CNC guy from the mfg company worked out a compromise design in the 36hp housing. Turns out the center-mount insert is capable of nearly equal cylinder bank volume and pressure ... but the 36hp housing will never be as equal.

We discover Porsche went to a center-mount blower housing for a reason. Here's our inspiration.

The problem is simple. The fan is offset in the housing and while you can compensate a lot with the vanes and ducting, the 1-2 cyl bank still gets the most air. Impeding the airflow on the 1-2 bank does not increase the flow to the 3-4 side.

Once we came to terms with the approx 60/40 air distribution, the issue became "Forget the 1-2 bank, are we able, via vane and ducting design, to get enough air to the 3-4 side so it runs about the same temp as the 1-2 side. Yes.

Head temp gauges and infrared temp readings showed we could. The baseline was equal temps on both heads. Oh boy did we open a can of tech worms working through this problem. Turns out 85.5 vs 94mm cylinders and heads read differently. Webers vs Solex (Kadrons) read differently. And to throw some mud in the game, 94mm Nikisil aluminum vs. 94mm cast iron cylinders obviously read differently.

Ignore the caption, it was for another purpose. Here, an engine and fan housing combo are being tested.

A surprise was the same engine on the test stand registered lower different overall temps from that engine in a car. Turns out the transaxle is a really effective heat sink. It makes me think we could benefit from transaxle oil coolers.

To conclude, we can now recommend you use the factory-type lower press-in air deflectors in your heads, and the upper cylinder tin deflectors that no aftermarket sheet metal provides. We get ours from http://www.awesomepowdercoat.com/

Our "fix" to the 60/40 airflow problem was our precise ducting to the 3-4 side. We substituted velocity for volume.

I am now really impressed! I don't think the older replacement housing really looked into the problem this closely. Good job team!

"We have a retired fluid dynamics engineer on staff, "Paul Ray The Rocket Scientist" who worked on NASA projects. He really didn't do anything with rockets, except for their launching facilities plumbing. He advises us on air scoops, oil system plumbing and their esoterics, ad nausem. If you want to get an hour lecture on a specific 90-degree AN fittings flow and swirl control, ask Paul Ray."

No thanks, I've sat for or had those discussions at my desk more than a few times. They can get very technical at times and a lot of it is important to know especially at some later time when other related issues come up. It sounds like your team was very thorough on the cause and effect of the design.

Is there any chance of making the centermount a stand-alone with a stand or plans?
CB has been sold out of the centermount kit ~since this started, and no indication if or when they will ever get more.
Last I heard the supplier had dissappeared.

I, for one, regularly embrace our new robot overlords, as I am the guy fixing the robots...